The death toll from H5N1 bird flu this year exceeded 36 million dead birds in the United States alone, reaching the same order of magnitude in France. Spain has ended the outbreak after recording a total of 31 outbreaks on farms in Andalusia and Castilla y Leon (affecting more than a million birds) and 37 outbreaks in wild birds in recent months.

Although this flu has a high bird mortality rate, most birds thought to be affected are killed before they become infected. The virus also does not currently pose a significant risk to humans.

Minor danger to human health.
Despite the high numbers of infected birds, only the second case of transmission to humans was identified last week, an American prisoner working on a macro farm. Infections in humans are extremely rare and only occur in close contact between humans and infected birds. The first case detected occurred in a British poultry industry worker who did not develop symptoms due to the infection.

According to the U.S. Centers for Disease Control and Prevention (CDC), more than 880 people have contracted the disease since 2003. Current strains of H5N1 are not as dangerous to humans as those seen in previous outbreaks. The main danger of these epidemics is that the virus mutates and infects humans and other mammals more easily.

Economic losses are not just for farmers.
The effects of these epidemics also have an economic dimension. One is its potential impact on inflation, as the US has warned of the rise in egg prices caused by these outbreaks. In addition to the estimated economic losses for farmers and insurers.

Control of the virus is therefore necessary not only to avoid possible harm to humans (health and economic) but also because of the damage the virus causes to birds. Not only is it fatal, it also causes respiratory problems, diarrhea and sometimes inflammation.

Arguments over victims.
In the United States, the means used to control this infection has caused some controversy, as farms often resort to a technique called vent shutdown (vent shut off), a method that involves raising the temperature of the enclosure in which birds are kept until they die from heat or excess CO2.

A process approved by US authorities during the avian flu epidemic that devastated country farms and killed 50 million birds in 2014-15. The level of industrialization of the breeding process in the American country creates an excellent breeding ground for the spread of the virus: On the one hand, due to the size of the livestock, which can reach one million birds; and on the other hand, because the low genetic diversity of birds makes them more vulnerable.

How does bird flu infect farms?
Once a case is detected on a farm, the infection can spread very easily on the farm, but it does not seem so clear how the first cases reached the farms. The culprits are usually wild birds. Direct contact between farm birds and wild birds is not necessary for these infections to occur. It is enough for the birds to fly over the environment so that the virus enters the livestock farms through their deposits.

Image | Aubrey Hicks Photography